In the radio communication technology field, a plurality of networks exist, for example, the second-generation communication (2G, Second Generation), third-generation communication (3G Third Generation), and long term evolution (LTE, Long Term Evolution) networks. Services based on the different networks include voice services and data services. Voice services are borne by the circuit switched domain (CS, Circuit Switched Domain), and are called CS domain services for short. Data services are borne by the packet switched domain (PS, Packet Switched Domain), and are called PS domain services for short.
The coverage of certain newly emerging networks among the preceding networks is not mature, and there may be no signal in these networks during actual use, affecting user experience. The following takes the 2G and 3G networks for example. Because the 3G network is an newly emerging network and is less mature than the 2G network, signal coverage of the 3G network is not so good as the 2G network. To improve user experience, terminals (such as 3G handsets) on existing 3G networks support 2G networks to help the terminals reselect 2G networks when the signals of 3G networks are weak. The terminals that support both 2G and 3G networks are called dual-mode terminals (typical dual-mode terminals include WCDMA/GSM dual-mode handsets and TD-SCDMA/GSM dual-mode handsets).
FIG. 1 is a structural schematic diagram of a common dual-mode terminal in the prior art. For easy description, the following lists only a plurality of major function modules, including:
a SIM card, a SIM card proxy module, an application, a service adaptation module, a 2G/3G protocol stack processing module, a 2G/3G physical layer processing module, a 2G/3G radio frequency processing module, and an antenna, where:
the SIM card is configured to store certain information of a user, including information indicating that the user is on a 2G network and a 3G network, for example, the SIM card can be a USIM card that is frequently used on the 3G network;
the SIM card proxy module is configured to perform a proxy service when the 2G/3G protocol stack processing module accesses the SIM card so that the 2G/3G protocol stack processing module can access the corresponding 2G or 3G user information in the SIM card on the 2G and 3G networks;
the application refers to applications related to services or control in the terminal;
the service adaptation module is configured to connect the application and 2G//3G protocol stack processing module, and select a proper protocol stack for transmitting services according to the camp state of the 2G/3G protocol stack;
the 2G/3G protocol stack processing module is configured to process 2G and 3G related protocols, where the protocols refer to protocols above the physical layer, for example, MAC, RLC, and RRC;
the 2G/3G physical layer processing module is configured to process protocols related to the 2G and 3G physical layers;
the 2G/3G radio frequency processing module is configured to perform processing functions related to 2G and 3G radio frequency modules; and the antenna receives and transmits 2G and 3G signals.
A single-card dual-mode terminal with the preceding structure preferably camps on a 3G network, and processes CS domain and PS domain services on the 3G network through modules such as 2G/3G protocol stack processing module, 2G/3G physical layer processing module, and 2G/3G radio frequency processing module.
When developing the present invention, the inventor finds at least the following disadvantages of the prior art:
When an existing single-card dual-mode terminal on a network reselects another network, a period in which services are unreachable exists. During this period, services are interrupted, and CS domain services and PS domain services cannot be performed, thereby affecting user experience.